The objective of the proposed work is to synthesize highly purified, well- characterized compounds that may have utility in the study of the biological processes involved in carcinogenesis. Some of the compounds may be carcinogens, e.g., nitrosamines such as the tobacco-specific carcinogen 4-(methylnitrosaminoI-(3-pyridyl)-l-butanone. Some may be metabolic intermediates,.e.g., 3,4-dihydro-trans-3, 4-dihydroxy-7, 12-dimethylbenz (a)-anthracene, which is an intermediate in the metabolic conversion of 7,12-dimethylbenz(a)anthracene to the potent ultimate carcinogen anti-1,2-anhydro-trans-3,4-dihydroxy-7,12-dimethyl1,2,3,4-tetrahydrobenz (a)anthracene. Some compounds may have demonstrated high mutagenicity and have a known exposure to humans but carcinogenesis data are lacking, e.g., the fecapentaenes, which occur in the feces of about 40% of the population on a western diet and are among the most mutagenic compounds known. The low concentrations found in the feces along with the high instability of the compounds make it virtually impossible to isolate sufficient quantities from natural sources to conduct studies that will determine the carcinogenic potency of the compounds.